When associated with the prostate, squamous cell carcinoma is very aggressive in nature. It is difficult to detect as no increase in prostate-specific antigen levels is seen, meaning that the cancer is often diagnosed at an advanced stage.

Cancer can be considered a very large and exceptionally heterogeneous family of malignant diseases, with squamous cell carcinomas comprising one of the largest subsets.[8][9][10] All SCC lesions are thought to begin via the repeated, uncontrolled division of cancer stem cells of epithelial lineage or characteristics.[citation needed] SCCs arise from squamous cells, which are flat cells that line many areas of the body. Accumulation of these cancer cells causes a microscopic focus of abnormal cells that are, at least initially, locally confined within the specific tissue in which the progenitor cell resided. This condition is called squamous cell carcinoma in situ, and it is diagnosed when the tumor has not yet penetrated the basement membrane or other delimiting structure to invade adjacent tissues. Once the lesion has grown and progressed to the point where it has breached, penetrated, and infiltrated adjacent structures, it is referred to as "invasive" squamous cell carcinoma. Once a carcinoma becomes invasive, it is able to spread to other organs and cause the formation of a metastasis, or "secondary tumor".

Keratoacanthoma is a low-grade malignancy of the skin. It originates in the pilosebaceous glands, and is similar in clinical presentation and microscopic analysis to SCC, except that it contains a central keratin plug. Statistically, it is less likely to become invasive than SCC.

Marjolin's ulcer is a type of SCC that arises from a nonhealing ulcer or burn wound. More recent evidence, however, suggests that genetic differences exist between SCC and Marjolin's ulcer, which were previously underappreciated.[12]

Adenoid squamous cell carcinoma (also known as pseudoglandular squamous cell carcinoma) is characterized by a tubular microscopic pattern and keratinocyteacantholysis.[13]

Basaloid squamous cell carcinoma is characterized by a predilection for the tongue base.[13]

Clear-cell squamous cell carcinoma (also known as clear-cell carcinoma of the skin) is characterized by keratinocytes that appear clear as a result of hydropic swelling.[13]

Signet ring-cell squamous cell carcinoma (occasionally rendered as signet ring-cell squamous cell carcinoma) is a histological variant characterized by concentric rings composed of keratin and large vacuoles corresponding to markedly dilated endoplasmic reticulum.[13] These vacuoles grow to such an extent that they radically displace the cellnucleus toward the cell membrane, giving the cell a distinctive superficial resemblance to a "signet ring" when viewed under a microscope.

SCC is a histologically distinct form of cancer. It arises from the uncontrolled multiplication of cells of epithelium, or cells showing particular cytological or tissue architectural characteristics of squamous cell differentiation, such as the presence of keratin, tonofilament bundles, or desmosomes, structures involved in cell-to-cell adhesion.

Studies have found evidences for an association between diet and skin cancers, including SCC. The consumption of high-fat dairy foods increases SCC tumor risk in people with previous skin cancer. Green leafy vegetables may help prevent development of subsequent SCC and multiple studies found that raw vegetables, citrus fruits and noncitrus fruits are significantly protective against SSC risk.[15][16] On the other hand, consumption of whole milk, yogurt, and cheese may increase SCC risk in susceptible people. [17] In addition, meat and fat dietary pattern can increase the risk of SCC in people without a history of SCC, but the association is again more prominent in people with a history of skin cancer.[18] Tobacco smoking and a dietary pattern characterized by high beer and liquor intake also increase the risk of SCC significantly.[19][15]